Muffler



Jan. 6, 1925. f 1,522,032

W. L. SCARFF MUFFLER Filed Aug. l5", 1921 2 SheetsiSeet 2 Wayna/Lkar shown my invention in 1n a manner now preferred by me.

Patented Jan. 6,l 1925.

WAYLAND L. SCARFF, F SEATTLE, WASHINGTON.

MUFFLER.

Application led August 15, 1921. Serial No. 492,393.

p To all whom t may concern.'

Be itfknown thatvI, VVAYLAND L. SCARFF, a citizen of the-United States, and resident of Seattle, King County, State of Washington, have invented certain new and useful Improvements in Muiilers, of which the following is a speciiication'.

y invention relates to muiiiers and particularly to muilerswhich are designed to be employed upon air-craft.

n important object of my invention is to produce a device which will muifle the sound vof a motor, without causing back pressure upon the motor.

A further object is to produce a muffler which will assist in the scavenging of the motor by reducing the back pressurel in the motor exhaust assages. v

A further ob' muffler of means for ,cooling the exhaust gases during their passage through the mufeL y My invention comprises those novel-parts and combinations thereof which lare shown in the accompanying drawings, described in the specification, and vparticularly defined by -the claimsterminating the same.

In theaccompanyin drawings I have rms and positioned Figure 1 is a perspective of my invention mounted upon an airplane.

Figure 2 is a plan sectional view of my device.

Figure 3 is an end from the forward end.

Figure 4 is an axial sectional view of a slightly modified construction.

It has been found diflicult to employ mufflers'in connection with air-craft motors on account of the back ressure caused thereby upon the motor. Mg invention is designed to serve as a muiiie'r and at the same time to reduce the back pressure upon the engine,

' and in this manner to assist in scavenging the engine. I accomplish this by providing in the muiermeans for producing a suction'upon' the exhaust gases from the engine so that they will be sucked through a more or less circuitous passage rather than. be forced through by the pressure remaining in the motor. I

I have provided a tubular casing 1 which serves as a combined discharge manifold and muiiier, conduits leading to the casing 1 view thereof taken ject is the provision in aI from the exhaust ports of the motor. The motor is not shown in the accompanying drawingsbut is to be understood as mounted beneath the hood 2 of the airplane fuselage 20, and a propeller 21 is rotated thereby.

The conduitsl() do not lead radially into the tubular casing .1, but rather extend at an angle to its axis, and all point towards an end 1l of the casing which is open and which is preferably restricted, for a purpose to be eplained hereafter. Preferably also, the conduits 10 lead. into the casing at a tangent thereto', as is best shown in Figure 3. This gives to the gases entering the casing from -the conduits a helcally whirling motion directed axially along the casing towards the open end l1. The opposite end l2 of the casing is closed.

Within the casing 1 is positioned av tapered air tube 3. This tube is open at both ends, and its smaller end 31 terminates adiacent the end '1l of the tubular casing 1.

Areferably the end 31 is positioned somewhat within the end 11 of the casing. The opposite end 32 of the air tube 3 being the larger end, extends at least to the closed end 12 of the casing. The end 32 might be flared or funnel shaped, but this will not be necessary in most cases, at least when used upon airplanes. It is sufficient that the end 32, which is generally the forward end of the muiiier, be somewhat larger than the end 31. In the modification shown in Figure 4, the air tube 3 has a vane 33 therein which is given a` quarter twist, to give the air passing through the tube 3 a slight helical twist. The tube 3 is shown as co-axial with the casing 1, and this is the preferred construction. Its end 3l may be supported by suitable braces 34 from the interior of the casing 1, or otherwise supported.

The muiiier is set upon an airplane preferably in the position shown in Figure l,

with the adjacent ends 12 of the casing and-32 of the air tube facing forward. Preferably also, the end 32 of the air tube is placed immediately rearward of the path of movement of the propeller tip so that the rearward blast thereof will force air through the tube 3. It may be found sufficient however, to .position the muifler so that the wind created by the` airplane in flight will pass through the air tube. It is conceivable that means other than the motion of the airplane for the propeller may be employedl to force a draft through the tube 3.

Air in assing through the tube 3 with any consi erable velocity is somewhat compressed by the time it reaches the restricted end thereof. In passin from this end 1t yexpands and. creates a sllght vacuum. This vacuum will react upon the air or gases within the annular space 13 between the casing l and the tube 3, inasmuch as the air tube terminates within the casing. This vacuum is transmitted through the conduits 10 and acts toV` relieve the backpressure in the conduits and upon the engine. The exhaus't gases passingl through the conduits 10 enter the annu ar space 13 ,and-are whirled helically therein as has been described. By thus passin through a more or less circuitous and enc osed passage, the sound thereof is 'greatly reduced. Moreover, by reason of the cooling eect of the surfaces of the tube 3 and the casing 1,

the exhaust gases are considerably cooled, and this also assists in relieving the back ressure upon the engine andl in the connits-10.

In the form shown in Figure 4, the vane 33 serves to give a whirling motion to the air passing through the tube 3 so that when the it emerges from the end 31 it is whirling similarly to the `whirling of the exhaust gases passin from the end l1.

There is t us no conflict of direction between the ure air and the exhaust gases. Care must taken however, not to create sufficient resistance in the air tube as to decrease materially the velocity of the air therethrough, as thiswould defeat onel of rincipal purposes of the muler by. building up back pressure in the muffler.

What I claim as my invention is:

' 1. In combination with an airplane, a motor, and a propeller, a motor muler including a tapered air suction tube, a tubular casing surroundingv said air tube, conduits'connecting the exhaust portsof said motor to said casing whereby they are affected by the suction of the air tube, and

said air tube being mounted upon the airplane with its large end forward, and` imwhereby the i of the mediately peller-tip.

2. An explosive engine muier comprising an air tube o en at both ends, its forward Vend being arger than the rear end, a casing surrounding said air tube, and forminfr an annular space therebetween, said annu ar space being closed at the lar end of the air tube and open at its sma end, the rear endI of said casing bein tapered down to a lrestricted openin disc arge gas conduits connected with said annular space and inclined with respect to the axis thereof whereb the gases enter said casing and move t erein 1n a helical path towards its rearward of the path of the proy rear end, and means in said air tube for producing a movement of air passing therethrou h 1n al like direction.

3. explosive engine muiler comprising an air tube olpen at both ends, its forward end being a a casing surrounding said air tube .and forming an annular space therebetween, said annular' space being closed at the large end of the air tube and open at its -small end, the rear end of said caslng bein tapered down to a restricted opening, disc arge gas conduits connected with said annular space and inclined with respect to the axis thereof gases enter said casing and move therein 1n a helical path towards its rear end, anda helicall twisted vane in the rear end of said air tu to direct air leaving said air tube in a direction correspond-l ing to that of the discharge said annular space.

4. In an airplane, in combination with a motor and a propeller, a motor muler comprising an open-ended air suction tube positioned immediately rearward of the path propeller tips, a gas tube associated with said air tube and having its discharge end .positioned within the zone of `influence gases leaving rger than the rear end,

sav

of the suction end of the air tube, and conduits connecting the exhaust ports of said motor tb said gas tube, whereby they are affected by the suction therein.` g Signed at Seattle, Kin County, Wash-- ington, this 23rd day of uly, 1921.

WAYLAND L. SCARFF. 

